The present invention relates to semiconductor devices, and particularly to forming e-fuse and precision resistor structures.
Many integrated circuits (“ICs”) are made up of millions of interconnected devices, such as transistors, resistors, capacitors, and diodes, on a single chip of semiconductor substrate. It is generally desirable that ICs operate as fast as possible, and consume as little power as possible. Semiconductor ICs often include one or more types of memory, such as CMOS memory, antifuse memory, and efuse memory.
One-time-programmable (“OTP”) memory elements are used in ICs to provide non-volatile memory (“NVM”). Data in NVM are not lost when the IC is turned off. NVM allows an IC manufacturer to store lot number and security data on the IC, for example, and is useful in many other applications. One type of NVM is commonly called an E-fuse.
E-fuses are usually integrated into semiconductor ICs by using a stripe (commonly also called a “link”) of conducting material (metal, poly-silicon, etc.) between two pads, generally referred to as anode and cathode. Applying a fuse current (IFUSE) to the E-fuse destroys the link, thus changing the resistance of the E-fuse. This is commonly referred to as “programming” the E-fuse. The fuse state (i.e., whether it has been programmed) can be read using a sense circuit, which is common in the art of electronic memories.